Method and apparatus utilizing the effects of cavitation in the treatment of fibrous suspensions

ABSTRACT

SUSPENSIONS OF FIBROUS MATERIALS ARE TREATED BY POSITIONING A NON-STREAMLINED SOLID CYLINDRICAL BODY, CROSSWISE IN A REACTOR SUCH THAT THE CYLINDER IS DISPOSED IN A HYDRODYNAMIC FLOW OF THE SUSPENSION TO PRODUCE A TWO DIMENSIONAL PLANE CONTRACTION OF THE FLOW. THIS CAUSES CAVITATION FORCES TO BE ESTABILISHED IN THE THUS CONTRACTED FLOW AND THESE FORCES ACT ON THE SUSPENSION TO EFFECT ANY ONE OR MORE OF VARIOUS TREATMENTS SUCH AS RESINATION, BEATING, BLEACHING, WASHING, ETC.

3,83%,982 THE EFFECTS OF cAvITATIoN; N THE TREATMENT or F'IBRoussusrznsrons 4 ROVICH ET AL US UTILIZIN p 10, 1974 R. ALEXAND METHOD ANDAPPARAT G Filed Sept. 1. 1972 .2 sheets-sheet 1 o 2 lm I m. no H 7% M CI a 2 .H ,U .m A Jfl M W 1 v y w M n 4 .H w w w A F a m w W 1:3: m? m Mw M I p 1974 R. ALEXANDROVICH EI'AL "8,834,982

IETHOD AND APPARATUS UTILIZING THE EFFECTS OF CAVITATION IN THETREATMENT OF FIBROUS SUSPENSIONS,

Filed Sept. 1, 1972 2 Sheets-Sheet a United States Patent 3,834,982METHOD AND APPARATUS UTILIZING THE EFFECTS OF CAVITATION IN THE TREAT-MENT OF FIBROUS SUSPENSIONS Rem Alexandrovich Solonitsyn, ulitsa AndreyaMalyshko 45, kv. 31, Kiev, U.S.S.R.; Ivan Elizarovich Vjukov,Grazhdansky prospekt 98, korpus 2, kv. 129; Leonid Alexeevich Gorbachev,ulitsa 3, Internatsionala 3, kv. 141; and Anatoly MikhailovichBelonogov, ulitsa Bela Kuna 23, kv. 171, all of Leningrad, U.S.S.R.; andGennady Afanasievich Vorobiev, Chuksin tupik 4, kv. and AlexandrVasilievich Efimov, ulitsa Starogo Gaya 6, korpus 1, kv. 58, both ofMoscow, U.S.S.R. Filed Sept. 1, 1972, Ser. No. 285,860 Int. Cl. D21b N00US. Cl. 162-1 19 Claims ABSTRACT OF THE DISCLOSURE Suspensions offibrous materials are treated by positioning a non-streamlined solidcylindrical body, crosswise in a reactor such that the cylinder isdisposed in a hydrodynamic flow of the suspension to produce a twodimensional plane contraction of the How. This causes cavitation forcesto be established in the thus contracted flow and these forces act onthe suspension to effect any one or more of various treatments such asresination, beating, bleaching, washing, etc.

This invention is concerned with a method of treating suspensions offibrous materials, such as pulp and its intermediate products,mechanical woodpulp and other fibrous materials used in the manufactureof paper, cardboard and cellulose derivatives, as well as with anapparatus for carrying said method into effect.

In the pulp-and-paper manufacturing practice, methods and devices areknown for effecting a number of technological processes associated withthe treatment of fibrous materials. Among them there are such processesas deresination of chemical and semichemical pulp, simultaneous beatingand deresination of chemical pulp and paper pulp, bleaching,chlorination and simultaneous beating and chlorination of chemical,semichemical and woodpulp, an enhancement of the reactivity andactivation of chemical pulp for the chemical processing thereof,acetylation of the chemical pulp, washing of the chemical pulp andwoodpulp, impregnation of plant fibres, deflocculation of wood pulpprior to casting on paperand cardboard machines, cleaning waste-waterfrom fibrous materials.

The prior-art methods of deresination of chemical pulp are effected byoxidizing resinous substances with oxygen or by removing the resintogether with small fibres by fractionation, or else by separating thesuperficial resin from the fibrous mass by the action of chemicalreagents with subsequent washing of the chemical mass on vacuum filters.The above-mentioned deresination methods, however, have found no Wideindustrial application in view of their inadequate efficiency. Thus,oxidation of resinous substances with oxygen involves fibre losses,considerable expenditures of chemicals amounting to 50 percent by weightof the fibre and a necessity of increasing production areas. The removalof resin from small fibres by fractionation with a sufficient extent ofderesination results in considerable fibre losses and calls for the useof rather complicated equipment.

Among the methods now in use the most effective proves to be that ofseparating the superficial resin from fibrous suspensions by anintensive intermixing thereof with chemical reagents. Even this method,however, features material disadvantages, since a required degreePatented Sept. 10, 1974 of deresination can be attained only with a highexpenditure of chemicals.

The known method of beating the chemical pulp with a concurrentderesination thereof is effected by crushing, cutting and brooming thefibres between the crossing bars of the beating equipment, with anintense intermixing of the fibrous suspension with chemical reagentsintroduced into the chemical pulp flow being treated before the beatingstage. In the process of beating the resin contained in thechemical-pulp fibres, depending on the chemical employed, either passesinto a dispersed state or coagulates and precipitates on the surface ofthe apparatus. Further the emulgated resin is removed from thetechnological treatment pulp flow with the use of washing apparatus, andthe resin deposited on the apparatus is removed therefrom either bywashing them with resin-dissolving agents or mechanically.

The now-existing methods for a concurrent beating and deresination arenot free from a number of disadvantages, viz. the beating process leadsto shortening of the fibre, and therefore high physico-mechanicalcharacteristics of the semifinished product can be attained only byincreasing specific consumption of energy for beating. Moreover, theresin deposited on the surface of the equipment, calls for the cleaningthereof so that the technological process should necessarily be of aperiodical character.

The known method of bleaching fibrous materials is effected by treatingthe fibrous suspension with bleaching agents, an intensive intermixingbeing a prerequisite. Complete interaction of the reacting components ismandatory. This condition, however, can be attained only by a longduration of the process, of the order of 2.5 to 3.5 hours and by the useof cumbersome equipment. Bleaching towers up to 30 m high and 6 mdiameter require great capital and maintenance investments. Essentialfluctuations in the quality characteristics of the resulting productgive rise to overexpenditures of costly chemicals due to a slow rate ofdiffusion processes on which the bleaching is based.

One of the known methods for bleaching fibrous suspension in a medium ofbleaching agents resides in ultrasonic treatment of such suspension.Ultrasonic bleaching ensures better conditions for the penetration ofthe bleaching agent into the material being treated, but this methodfails to find industrial applications due to high power consumption andlow efficiency of ultrasonic converters.

The process of chlorinating the chemical pulp prior to bleaching thereofis aimed at oxidizing the lignin contained in the chemical pulp byelementary chlorine. In this respect it is common practice to mix thechemical pulp suspension with gaseous chlorine. The process efficiencyand the quality of the resulting product depend on the intensity ofmixing the chemical pulp with chlorine and on the uniformity with whichthe latter is distributed in the suspension. Known in the art is amethod of kinetically mixing the chemical pulp with chlorine inaerators; this method, however, suffers from a number of disadvantagesresiding in a considerable consumption and incomplete utilization ofchlorine, high costs of equipment and complexities in the manufacture ofaerators.

The processes of bleaching and beating the suspension of fibrousmaterials can be combined by subjecting the fibrous material to asimultaneous action of bleaching agents and mechanical treatment inbleaching apparatus. Such a procedure, however, failed to find any wideindustrial application due to high power consumption and lack ofappropriate equipment.

A known method for enhancement of the reactivity of the chemical pulpintended for further chemical processing is effected by treating itsfibres either chemically or mechanically. The main problem to be solvedin the production of high-reactivity chemical pulp resides in ensuringmost complete destruction of low-reactivity sheathings of the fibres andloosening of the cell membrane structure. Such chemical pulp, in thecourse of chemical processing thereof, exhibits higher ability offorming viscose solutions. It is known to increase the pulp reactivityby refining it on a Jordan mill prior to casting on press machines. Thisprocess, however, requires thorough control for precluding shortening ofthe fibres and disturbance of their adsorption properties. A method isknown for increasing the reactivity of the chemical pulp by treating itin an ultrasonic field; but industrial applications of ultrasonictreatment procedures prove to be excessively expensive. It should alsobe pointed out that ultrasonic treatment of chemical pulp suspensionsproduces rather weak effects on the structure of cell membranes of thefibres.

Thus, a noticeable increase in the reactivity of the chemical pulp bytreating the pulp suspension with the use of ultrasonic techniques witha frequency of 400 kHz. can be attained only after a period of 30 to 60min, with the suspension concentration being not higher than 0.32 to0.325%.

With the frequency of the treatment brought down to 20 or 30 kHz. andintensity more than 5 v./cm. and the same period of treatment, theconcentration of the suspension being treated has to be reduced to 0.l0.2%.

For enhancing the intensity of ultrasonic effects, investigations werecarried out as to the possibility of treating the suspension under highstatic pressures; this, however, makes the process equipment morecomplicated and the process itself becomes less effective.

Known in the art is a method of increasing the reactivity of thechemical pulp by treating the suspension by means of an electrohydraulicshock. This method of electrohydraulic treatment is based on theorigination of shock waves and displacements with an electric spark-overin a liquid. Hydraulic pulses originating due to an electric dischargein the liquid consist of two shocks. The first, which is the main andmore powerful one, is a hydraulic shock whose shape is similar to thatof current pulses; the steeper the pulse and the higher the amplitude,the shorter and more powerful the main hydraulic shock is. The mainhydraulic shock is accompanied by side eifects, butthe main destructiveforce in the electrohydraulic effect is attributable to the hydraulicshock. The electrohydraulic shock is a powerful means for treatingmaterials in a liquid and therefore currently it is known to be usedmainly in metal working. Thus, electrohydraulic devices are known forknocking out cores from castings. As to the treatment of chemical pulp,there is a danger that the fibre could be simply destroyed, thisproducing a deleterious effect on the properties of the pulp thusprocessed. It is therefore necessary to control the force and depth withwhich the chemical pulp fibres are treated and obviate particularlystrong effects on the fibre structure. To this end, it is necessary tomake use the minimum limit of the permissible power of theelectrohydraulic effect, this, however, being inexpedient from both theeconomical and technical standpoint.

The known method of activation of the chemical pulp for any kind ofchemical processing, such as production of cellulose acetate, viscoserayon, nitrocellulose, cellulose ethers, fibre and other products,comprises singleor two-stage cooking of woodpulp, followed by multistagecleaning and single or multistage refining. Said sequence of operationsensures the required chemical composition of the resulting cellulose,but the latter is far from being always well processable and givingfinished products of an adequate quality. Besides chemical composition,the supramolecular structure of the chemical pulp, a looser or denserstructure of its macromolecules prove to be decisive for the chemicalprocessing thereof.

Laboratory methods are known in the art for activating the chemical pulpby inclusion techniques. In accordance therewith, the chemical pulp isallowed to swell in water or alkali and then the latter is displaced bya polar liquid (such as acetone or methanol), for which purpose the pulpis Washed with a 5 to 20-fold volume of the last-mentioned agents. Thelatter agent is likewise displaced but with a non-polar liquid such asbenzene, for which purpose the chemical pulp is washed With anapproximately equal amount of this solvent. The above method requiresthe use of several agents in a quantity considerably exceeding theweight of chemical pulp and therefore this method failed to findindustrial application.

It is known to activate the chemical pulp by vacuum inclusion withglycerol; but complexity of the process equipment and high powerconsumption associated therewith are also a hindrance for the industrialimplementation of such process.

One of the present-day methods of acetylating the chemical pulp consistsin treating the mixture being acetylated with the use of ultrasonics.This method allows the obtaining of a final product featuringsufliciently high physical and chemical homogeneity with a lowerconsumption of chemicals. But the complexity of ultrasonic devices, highspecific power consumption conditioned by a low efficiency of thedevices and low output capacity are essential disadvantages inherent inthis acetylation method.

The known method of impregnating plant fibres with solutions of chemicalagents widely employed in pulp and paper industry such as impregnationof chopped cane and straw or wood chips is conducting while coo-king.The impregnation depth is vital for the quality of the resulting productand for the uniformity of treatment of the plant fibres. When immersedinto the impregnating liquid, wood tracheids, bast fibres of choppedcane and straw, plant fibres of semifinished products behave as a systemof deadended capillaries. Air contained in the fibres offers the mainobstacle to the impregnation of material. The air contained in the fibrecapillaries is urged by the impregnating liquid further into the fibreand the air thus compressed oifers an increasing resistance to theimpregnation. Air dissolution is a lengthy process and therefore deepimpregnation of fibres is possible only when there is no air in thecapillaries thereof.

There exist a number of impregnation methods envisaging only partialremoval of air from fibre capillaries with the use of vacuum techniquesor preliminary steam treatment of the material. Vacuum techniques areeffective only with a definite moisture of the material, require highlytight equipment, involves higher power consumption and greater number ofoperations in the process. Preliminary steaming of the material undertreatment leads to a dilution of the Working solution, to higherconsumption of steam and greater time required for the entire processand also requires high uniformity of the steam treatment.

The known method of washing the chemical pulp after the treatmentthereof with solutions of chemicals when manufacturing paper cardboardand cellulose derivatives in the course of chemical processing isperformed by diluting the suspension of fibrous material with water,intensive stirring thereof and subsequent dehydration to a definiteconcentration. The chemicals contained in the fibres pass into thesolution which is separated at the dehydration stage. The quality of theWashing is very important, and in some cases even proves to be decisive.For example, when preparing cellulose nitrates, thorough washing is adecisive factor for the required quality of the finished product. Inthis case even traces of acids remaining after the washing render thechemical pulp unfit for storage.

With the above-described methods of washing the process takes from 8 to10 hours with the washing water repeatedly changed and the fibresmechanically agitated.

The washing can also be performed with the use of ultrasonic techniques.With a high flow rate, however, such washing technique is quitecomplicated and economically unreasonable.

The known method of mercerizing cellulose fibres when preparing spinningsolutions is effective by mixing these fibres with a caustic sodasolution. Both periodic and continuous action apparatus are used for thepurpose, the promising being that which ensures continuous mercerizationof the cellulose, the process being run with the cellulose continuouslymixed with caustic soda. The main disadvantage of the known methodresides in that fails to ensure rapid and uniform diffusion of thereagent into the fibre.

The most important stage of the technological process for thepreparation of viscose rayon is known to be not only mercerization butalso dissolution of cellulose xanthate. The dissolution processconditions are decisive for the quality of viscose rayon and are to agreat extent responsible for the ultimate properties of the rayonproduced. Incomplete dissolution, inhomogeneity of the viscose rayoncause considerable difficulties for the maturing and filtering thesolution, as well as for shaping the fibre.

Cellulose xanthate can be dissolved by making use of additionalmechanical effects such as crumbling, agitation and crushing it, orsubjecting it to ultrasonic treatment. The now-existing methods takefrom 3 to 5 hours for their accomplishment, and ultrasonic treatment iseconomically inexpedient.

The known method of dyeing the paper pulp and introduction of fillers iscarried out with the suspension of fibrous materials being intermixedwith the pigments introduced thereinto. It is most preferable to makeuse of mineral pigments such as titanium dioxide, red oxide, lead yellowmolybdate, raw umber, and the like. Wide industrial application of thispigment, however, is limited due to poor dispergation of the aggregatedparticles and nonuniform distribution of the dye in suspension with ahigh number of visible inclusions of dye particles over 35-40 micron insize. Poor distribution of certain dyes in the suspension of fibrousmaterials is caused by the presence of strong agglomerates of pigmenttherein, which cannot be dispersed under stirring.

Methods are known in the art for dispersing and stirring the colorantswith the use of ultrasonic treatment and also by intermixing withsurfactant additives. However, the use of surfactants causes foaming ofthe fibrous suspension which results in poor properties of paper whileultrasonic treatment renders the process materially more expensive.

Defiocculation of the paper pulp before casting on a paper machine is animportant stage of final preparation of a homogeneous fibrous suspensionwhen making highquality paper, such as condenser paper and paper ofother special grades. Usually deflocculation of the paper pulp iseffected by passing the fibrous suspension through narrow elongatedslits in a metallic knot catcher screen. Agglomerated fibres left on thescreen are removed from the process and further directed for utilizationin paper of inferior grades or are disposed of as waste. Deflocculationof the paper pulp is also performed in the process of dispersing fibreagglomerates by subjecting the suspension to highfrequency oscillations.A method of treating the pulp in centrifugal-pulsation apparatus hasbecome most widespread in industry. The generation of oscillations inthe suspensions by the known methods for the realization of the aboveprocess suffers from a number of disadvantages such as complexity ofapparatus design, inadequate quality of cleaning and a possibility ofagglomerate formation after the cleaning, as well as high maintenanceand service costs and low efficiency of the existing method. A methodfor cleaning waste water from fibrous mass by flotation is widelyemployed in the pulp and paper industry. The known method is based onair flotation residing in the action of molecular forces contributing tothe adhesion of emulgated, fine disperse and other substances with airbubbles introduced into the waste water. Air bubbles floating up to thesurface of the waste water make up a foam-like layer saturated with thesubstance being floated. In the flotation process use is made ofchemical additives promoting foam formation and conferring to thesubstances being floated an ability of sticking to the air bubbles,thereby expelling them from the water.

For the flotation process to be effective it is necessary that wastewater should be energetically agitated and saturated with air bubbles inthe presence of flotation chemical additives. The methods of cleaningwaste water by flotation now in use have a number of disadvantages,these being lengthy flotation periods coming to 10l5 minutes, highconsumption of flotation reagents of from 5 to 50 g. per cu. in. water,low degree of clarification (to 96%), and a low concentration ofsubstances in the fioatant (0.5 to 1.0%). The realization of thesemethods require expensive and complicated apparatus. These methodscannot cope with the large amount of waste water to be cleaned.

Known at present is the use for treating liquids of cavitation forcesarising in the hydrodynamic flow of the liquid (cf., e.g., the materialspertinent to FRG application No. 1,557,212; Cl. 12c, 4/01 of May 26,1967).

The cavitation arising in the liquid flow is used for intermixing liquidpulverized and gaseous components. The liquid treatment is accomplishedby the creation of cavitation with the liquid being passed through a jetnozzle and another component being supplied into the cavitation zonecharacterized by a high vacuum. The device for realization of suchmethod is made as a conventional injector. These methods and devices,however, are inapplicable for treating suspensions of fibrous materials,since cavitation forces arising in such hydrodynamic flow are of lowintensity. The embodiment of the contraction mem her as a jet nozzleprovides for a volumetric one-dimensional contraction of the flow with aperiodic recurrence of vortex flow separation. Though with such flowaround body cavitation takes place its erosion activity is negligiblysmall.

The erosion activity is used here and hereafter to imply the intensityof cavitation to erosion effect.

A number of experimental and theoretical investigations in the field ofcavitation have proved the erosion activity of cavitation to be in anexponential dependence from the value of the pressure pulsations withinthe cavitation zone. The pulsation of pressures in its turn also dependson the form of the flow restriction and kind of the body within theflow. The cavitation resulting due to the constriction of the flow bythe jet nozzle is weak and sufiices only for intermixing any givencomponents in the liquid. Moreover, injection of some other componentinto the cavitation zone disturbs its structure, the degree of vorticityof the cavitation void, and leads to a considerable decrease in theStrouhal vortex wake number. This still further reduces the erosionactivity of cavitation.

It is likewise a well-known fact that supplying gaseous components intothe cavitation zone is undesirable, since it brings about a change inthe very character of the cavitation process and a diminution of theerosion activity to zero.

It is clear from the above-stated that the application of cavitationwhich originates in a hydrodynamic flow of injector devices for treatingsuspensions of fibrous materials is impossible in view of low erosionactivity of such cavitation.

It is an object of the present invention to provide a method of treatingsuspensions of fibrous materials which would allow intensification ofvarious technological processes conducted in the pulp-and-paperindustry.

Another object of the invention is to provide an apparatus for treatingsuspensions of fibrous materials, which, while being simple in design,features high output capacity, low power requirements, and ensures apossibility of the cavitation field intensity to be controlled within awide range.

Among those various processes performed in the pulpand-paper industrythat can be intensified by the method of the invention, deresination ofthe chemical pulp, bleaching of woodpulp and chemical pulp, chlorinationof chemical pulp, increasing of the reactivity of chemical pulp forfurther chemical processing thereof, simultaneous beating andderesination of chemical pulp,-simultaneous beating and bleaching ofchemical pulp, activation and acetylation of the chemical pulp forfurther chemical processing thereof, impregnation of fibrous materials,washing of the chemical pulp, mercerization and dissolu tion ofcellulose xanthate, dyeing of the paper pulp, cleaning of waste waterfrom fibrous materials and deflocculation of the paper pulp, and otherscan be mentioned.

The above and other objects are accomplished in that when treatingsuspensions of fibrous materials by subjecting the suspension to theaction of cavitation forces that are created in a contractinghydrodynamic flow of the suspension to be treated, according to theinvention, the cavitation forces in the hydrodynamic flow of thesuspension being treated are created by immersing in said flow of atleast one solid that causes a two-dimensional plane contraction of thesaid flow.

For the deresination of fibrous materials, dispersing agents can beintroduced into the suspension flow, upstream the contraction thereof,in an amount of 0.5 to 1.0 percent by weight of the fibre, it beingadvantageous to combine the procedures of the deresination and beatingof the fibrou materials.

For the bleaching of fibrous materials, bleaching agents can beintroduced into the suspension flow upstream the contraction thereof, itbeing advantageous to combine the procedures of bleaching and beating ofthe fibrous materials.

For chlorinating the fibrous materials, gaseous chlorine can beintroduced into the suspension flow upstream of the contraction thereof.

For increasing the reactivity of the fibrous materials, surfactants canbe introduced into the suspension flow upstream the contraction thereof.

For activating the fibrous materials, inclusion agents can be introducedinto the suspension flow upstream the contraction thereof.

For acetylating the fibrous materials, a catalyst can be introduced intothe suspension flow upstream the contraction thereof.

For impregnating the fibrous materials, an impregnating cooking liquorcan be introduced into the suspension flow upstream the contractionthereof.

For washing the fibrous materials, water can be introduced into thesuspension flow upstream the contraction thereof.

For mercerizing the fibrous materials, alkali can be introduced into thesuspension flow upstream the contraction thereof.

For dissolving cellulose xanthate, a solvent can be introduced into thesuspension fiow upstream the contraction thereof.

For dyeing the fibrous materials, a pigment can be introduced into thesuspension flow upstream the contraction thereof.

For cleaning Waste water from fibrous materials, air can be introducedinto the suspension flow upstream the contraction thereof.

The above and other objects are also accomplished in that in anapparatus for treating suspensions of fibrous materials, comprising areactor having a shell accommodating a member for contracting the flowin the suspension of fibrous materials pump-fed along a system of pipes,and for creating cavitation forces in the suspension, said memberaccommodated in the reactor shell and adapted for being immersed intothe suspension flow,

is shaped as a cylinder and arranged near the entrance portion of thereactor equidistantly from the side walls thereof in such a manner thatthe line generating the cylindrical surface of said member is normal tothe direction of the suspension travel; the reactor from the side of thesuspension entrance being associated with the system of pipes by meansof an eifuser and from the side of the suspension exit, by means of adiffuser.

Moreover, at the olfuser entrance, over the periphery thereof, nozzlescan be provided for supplying chemical agents into the flow of thesuspension of fibrous materials. For increasing the erosion activity ofthe cavitation forces, the cylindrical surface of said member immersedinto the suspension flow can be coated with a layer of elastic material,or, else, a vibrator can be arranged in the reactor past the saidcylindrical body coaxially therewith.

For measuring the erosion activity of the cavitation forces it ispreferable that a pickup unit should be arranged in the reactor.

The essence of the present invention resides in the following.

The prior-art methods are based on the use of hydrodynamic cavitation inthe flow of the suspension of fibrous materials, this cavitationoriginating in the place of the flow contraction as the suspension movesaround bodies of a certain shape, the latter inducing the cavitation.

Cavitation cores are bubbles of air present in the micro- -macro-,submicropores and capillaries of the fibres. With a sharp pressure droppast the member immersed in the flow, the cavitation cores grow tobubbles from 0.1 to 1.0 mm. in size, while in the increased pressurezone the dimensions of the cores sharply diminish. With the bubblesenclosed within the cavitation void, shock waves of score thousands ofatmospheres originate in the microvolumes of the suspension. Thesepulses cause repeated deformations of the fibres. The fibre walls becomedelaminated and fibrillated, this contributing to the development of theactive surface area of the fibre and, hence, to a more rapid penetrationof the chemical agents into the fibre. The fibres that have undergonethe cavitation effect easily react with other components introduced intothe suspension and therefore the reaction speeds of the process are infact determined by the speeds of the chemical reactions proper.

The cavitation forces are manifested in the action of instantly changingpressure gradients, in intensive stirring under the effect of shockwaves and microfiows, and are thus responsible for the erosion activitywith respect to the suspension being treated. Therefore the creation ofan erosion-active stage of cavitation in the hydrodynamic flow of thesuspension being treated is of great interest.

According to the invention, for inducing the cavitation, it is suggestedthat a non-streamlined cylindrical solid should be arranged in thecontracting hydrodynamic fiow.

As is known, such a flow features plane two-dimensional vortex wakeswhich extend over the entire cross-section of the suspension flow. Thevoid has maximum vorticity which determines the degree of rarefactionthereof, and the vortex wakes in case of the cylindrical solid arestrictly periodic in obeyance with the Strouhal number. The abovefeatures taken in combination determine the maximum erosion activity ofthe cavitation void. The cavitation caused by the flow moving around thecyllindrical member arranged across the path of the suspensioncorresponds to the plane two-dimensional vortex wake.

Investigations have shown the erosion activity of the hydrodynamiccavitation created by solids of other shapes to be 8 to 12 times lessthan that observed in the wake past the cylindrical solid.

It should be pointed out that the intensity of cavitation in. thetwo-dimensional plane flow can be increased in case the amplitude ofpulsations of the Strouhal number is actively changed by superimposinginto the field of 9 hydrodynamic pulsations an additional pulsesynchronous with said field.

The erosion activity of the hydrodynamic flow cavitation whichoriginates when the flow is contracted by the cylindrical body exceedsthe intensity of cavitation induced by other known methods.

Insofar as the potential cores of cavitation are located directly withinthe fibres, this particular circumstance makes it possible, under theconditions which cause hydrodynamic, separation or flow cavitation (andonly such cavitation), easily effect stripping of low-reactivity layersof the cell membrane and thus increase the active surface area of thefibres without the accumulation of low-molecular fractions.

The selectivity of the process is favored by the structure of thechemical pulp fibres, since the primary membrane (low-reactivity layer)is more porous than the inner layer of the secondary membrane, While theouter layer of the secondary membrane is more porous than the innerlayer of the secondary membrane.

Thus, in the present invention both the specific features of the veryprocess of hydrodynamic flow cavitation and those of the material to betreated are used to advantage.

The investigations carried out concerning the changes in the structureof the cell membrane of the chemical pulp have confirmed higheffectiveness of the present method for treating fibrous materials.

An apparatus for the realization of the present method is disclosedhereinbelow.

The apparatus of the invention, wherein cavitation is made to take placewill be here and hereafter referred to as a reactor. A specific featureof the present reactor resides in employing the erosion activity of thecavitation which originates in the wake past the cylindrical solidimmersed in the flow. As has been pointed out above, such cavitationfeatures maximum erosion activity.

The reactor is essentially a pipe rectangular in cross section, so thata member adapted to contract the suspension flow can easily be arrangedtherein. This cylindershaped member is arranged close to the entranceportion of the reactor, equidistantly from the side Walls thereof, insuch a manner that the line generating the cylindrical surface of saidmember is normal to the direction of the suspension travel. Sucharrangement of the cylinder provides for periodic formation of vorticesin the plane two-dimensional suspension flow and for a free space in thereactor necessary for the creation of the required structure of thecavitation void.

An effuser and a diffuser associate the reactor with a system of pipesand ensure smooth motion of the suspension flow along the reactorwithout any additional hydraulic resistance.

Nozzles for supplying chemical agents are arranged at the effuserentrance over the periphery thereof in such a manner that they do notinterfere with the cavitation zone structure and thus increase theerosion activity of the cavitation.

The coating of the cylindrical member surface with elastic material andprovision of a vibrator in the reactor increase the erosion activity ofthe cavitation, since superpostion of additional pulsations of thecavitation void vortices onto the cavitation field, these pulsationsbeing synchronous with said field, actively increases the amplitude ofnatural pulsations characterized by the Strouhal number.

A pickup arranged in the reactor for measuring the erosion activity ofthe cavitation field serves to determine optimum parameters of thehydrodynamic flow.

Given below is a detailed description of an exemplary embodiment of anapparatus of the present invention to be considered in conjunction ofthe accompanying drawings, wherein:

FIG. 1 is a schematic view of an apparatus for treating the suspensionof fibrous materials;

FIG. 2 is a reactor of the herein-proposed apparatus as viewedsubstantially in a longitudinal section thereof; and

FIG. 3 is an alternative embodiment of the reactor.

The apparatus represented in the drawings, comprises: a reactor 1 (FIG.1), a pump 3 communicating therewith via a pipe 2, a tank 5 for thesuspension under treatment to recirculate, said tank communicating withsaid pump via a pipe 4, and an overflow tank 6 communicating with thetank 5 via a pipe 7. The reactor 1 communicates with the overflow tank 6via the pipe 2 which incorporates an upright run 8. The overflow tank 6communicates with a finished-product tank 10 via a pipe 9.

A rectangular cross-section shell 11 (FIG. 2) of the reactoraccommodates a non-streamlined cylindrical member 12 located nearby theentrance thereof at equal distances a from the lateral walls of theshell. The element 12 is so positioned that the generatrix of itscylindrical surface is normal to the direction of the suspension flow(as indicated by the arrow A).

At the inlet of the suspension the reactor shell is connected to aneffuser 13, and at the outlet thereof, to a diffuser 14.

Provided at the entrance of the effuser 13 around the periphery thereofare nozzles 15 for chemical reagents to feed into the flow of thesuspension of fibrous materials.

An alternative embodiment of the reactor makes provision for a coating16 (FIG. 3) on the cylindrical member 12 made of an elastic material,e.g., rubber as well as for a vibrator 17 located beyond the cylindricalelement 12 and extending longitudinally along the reactor center line.

Provision is also made in the reactor 1 (FIG. 1) for a hydrophone pickup18 adapted for measuring with its analyzer 19 the erosion activity of acavitation field.

The apparatus described above operates as follows.

The fibrous suspension of the material under treatment, taken in aconcentration of up to 8 percent is fed along a pipe 20 (FIG. 1) to therecirculation tank 5, wherefrom the suspension is fed via the pipe 4into the pump 3 and, under a pressure of 30-40 m. H O developed by thepump, is fed along the pipe 2 through the efiuser 13 into the reactor 1.Through the nozzles 15 located in the effuser, chemical reagents areintroduced into the flow of the suspension. At the place of expansion ofthe previously contracted flow, a hydrodynamical cavitation field isestablished which renders an intensifying effect upon the fibrousmaterials under treatment. The suspension of fibrous materials treatedin the reactor, is fed via the diffuser 14 and the pipe 2 incorporatingthe upright run 8, into the overflow tank 6. Therefrom part of the flowin suspension is passed along the pipe 9 into the finishedproduct tank10, while the main flow in suspension is directed to recirculation alongthe pipe 7 into the tank 5. The thus-treated suspension from the tank 10is fed into the production cycle as indicated by the arrow B.

The degree of treatment of the suspension depends upon the adopted valueof the recirculation factor according to which the pump delivery rate isselected.

The intensity of the cavitation field in the reactor is determined bymeans of the intensity analyzer 19 which receives a signal from thehydrophone pickup 18.

The intensity of cavitation is adjustable by varying the height of theupright run of the pipe 8. By appropriately altering the height of thecolumn of the flow in suspension or the parameters thereof, one canattain such a value of the pressure effective in the reactor, thatenables a cavitation field possessing the optimum erosion activity to beobtained.

The operating principle of the analyzer is based upon the fact that themaximum sound pressure measured by the instrument is directlyproportionale to the erosion activity of a cavitation field.

When practicing some methods of the treatment of the fibrous suspension,such as increasing its reactivity, it is recommendable to increase theerosion activity of the 1 1 cavitation field which is renderedpracticable with the use of the reactor illustrated in FIG. 3.

The erosion activity of cavitation in such a case may be enhanced by 6-8times, this being attained with the total capacity of the apparatusremaining the same.

The apparatus illustrated in FIG. 1 is applicable in a technologicalprocess for carrying out operations involved in the treatment of thesuspension of fibrous materials.

Given below are a number of specific exemplary operating conditions andparameters of some techniques employed in pulp-and-paper productionpractice for the treatment of the suspension of fibrous materials.

EXAMPLE 1 Let us consider an exemplary embodiment of the treatmentprocess of the suspension of fibrous materials involved in deresinationof the bleached hardwood sulphate pulp. The fibrous suspension of saidmaterial taken in a concentration of up to percent, is pump-fed into thereactor. A hydrodynamic cavitation field is established at the place ofthe flow contraction, which exerts its influence upon the extraction ofresin from the fibre and emulsification of the former in a liquidmedium. To reduce time spent for the deresination process, it ispracticable to introduce some dispersing agents (taken in an amount of0.5 to 1.0 percent of the total weight of the fibre) into the suspensionupstream of the contraction of the flow thereof. As a result, the numberof recirculation cycles of the suspension through the reactor may bereduced to 5 times.

As a result of the treatment by the herein-proposed method a 30-to-6Opercent decrease in the content of resin in the pulp is attained,whereas the known methods reduce the resin content but by -15 percentwith the same power consumption rate.

EXAMPLE 2 Let us consider an exemplary embodiment of the treatmentprocess of fibrous materials for a simultaneous beating and deresinationof the unbleached sulphite pulp. The fibrous suspension in aconcentration of up to 4 percent is pump-fed from the recirculation tankinto the reactor. At the place of contraction of the flow in suspensiona hydrodynamic cavitation field is established which producesfibrillating action upon the fibrous material to facilitate extractionof resin particles therefrom. The suspension recirculates through thereactor -20 times with the result that emulsification of the particlesof resin occurs without adding chemical dispersing agents. Prior tobeing used in further production processes, the suspension of fibrousmaterials is dehydrated by a conventional method to a concentration of6-7 percent.

As a result of the treatment by the proposed method, a 30-40-percentdecrease in the pulp resin content, 2 to 3 SR increase in the beatingdegree and a S-percent increase in certain physico-mechanicalcharacteristics are attained.

EXAMPLE 3 Let us consider an example of carrying into efiect thetreatment process of the suspension of fibrous materials for bleachingthe mechanical woodpulp. The fibrous suspension of that material takenat a concentration of 4 to 6 percent is pumped from the recirculationtank into the reactor. A hydrodynamic cavitation field is created at theplace of contraction of the suspension flow to intensify the bleachingprocess. The components of the bleaching compound are introduced during1.0-1.5 minutes through the nozzles located in the effuser, viz, sodiumsilicate, hydrogen peroxide and caustic soda. The latter is introducedin two steps with an intermediate checking the pH value of the mediumuntil it reaches 10.2.

Control of the bleaching process, i.e., an increase in the whiteness ofthe woodpulp, is exercised by way of determining the whiteness ofcastings against the Zeiss leucometer.

The total duration of the bleaching process is 15 minutes at asuspension temperature of 45-50 C.

As a result of the treatment by the proposed method, the bleaching timeis reduced 12-16 times and the degree of whiteness is increased by 5.5units as compared to the now-existing bleaching methods, otherwiseconditions being identical.

EXAMPLE 4 Let use consider an embodiment of the treatment process offibrous materials for chlorination of sulphite pulp.

T he fibrous suspension of the material under treatment with aconcentration of 3-4 percent at a temperature of 15-20" C. is pumpedfrom the recirculation tank into the reactor.

A hydrodynamic cavitation field is established in the reactor at theplace of contraction of the suspension flow to intensify thechlorination process.

Gaseous chlorine is uniformly fed through the nozzles located in theeffuser throughout the chlorination process. The recirculation factorduring the pulp chlorination process is from 15 to 20.

As a result of the treatment by the proposed method,

the general chlorination stages are reduced two times, theconsumption ofchlorine and the chemicals used at the stages of bleaching and refiningof said pulp is substantially diminished. The increase in whiteness by2-5 units is accompanied by enhanced physico-mechanical characteristicsby 4-6 percent and a 30-percent decrease in the degree of dirtiness.

EXAMPLE 5 Let us consider an exemplary embodiment of the treatmentprocess of fibrous materials for simultaneous bleaching and beating ofsulphite pulp.

The fibrous suspension of the material under treatment with aconcentration of 3-4 percent at a temperature of 40-50 C. is pumped fromthe recirculation tank into the reactor.

A hydrodynamic cavitation field is established in the reactor at theplace of contraction of the suspension flow to intensify the bleachingprocess and concurrently fibrillate the fibrous suspension. The numberof recirculation in this case amounts to 10-15. 1

Bleaching chemicals are fed through the nozzles located in the efiuser.Upon treatment in the hydrodynamic cavitation field the pulp is washedby a conventional method.

As a result of the treatment by the proposed method, a 5-6 percentincrease in the physico-mechanical characteristics of the finishedproduct and an increment of whiteness by 9 units are obtained.

EXAMPLE 6 Let us consider an exemplary embodiment of the treatmentprocess of fibrous materials aimed at increasing the reactivity of thepulp.

The fibrous suspension of the pulp to be chemically processed, taken ata concentration up to 4 percent and a temperature of 20 to 30 C., ispumped into the reactor.

A hydrodynamic cavitation field is established at the place ofcontraction of the suspension flow to exert influence upon the materialunder treatment. The number of recirculation in this case amounts to25-30.

As a result of the treatment by the proposed method, an increase in thepulp reactivity from /11 percent CS /NaOI-I attainable by thenow-existing method, to 60/11 percent Cs /NaOH, the resultant cellulosexanthate being essentially a transparent and fast-to-filter viscosesolution.

Examinations of the fibre microstructure have proved also that itstreatment in the hydrodynamic cavitation field is conducive to anintensive elimination of the unreactive layers of the cell wall and auniform fibrillation of the fibre surface.

13 EXAMPLE 7 Let us consider an exemplary embodiment of the treatmentprocess aimed at activating sulphate and sulphite refined pulp.

The fibrous suspension of the pulp with a concentration of 26 percent ata temperature of 4050 C. is pumped from the recirculation tank into thereactor, the number of recirculation amounting in this case to 25-30. Ahydrodynamic cavitation field is established at the place of contractionof the suspension flow to exert influence upon the material undertreatment.

Fed through the nozzles in the etfuser is an inclusion agent taken as a3-percent glycerol solution in an amount of 2.0 to 5.0 percent of thefibre weight.

Upon dehydrating the pulp on filters, the inclusion agent is againintroduced into the production cycle to further circulate therein.

Treating the pulp in the cavitation field in the medium of the inclusionagent consists in loosening its supramolecular structure so as toincrease the accessibility of the macromolecules thereof.

As a result of the treatment by the proposed method, the followingcharacteristics are attained which are compared with those resultingfrom the now-existing activation methods: viscosity, 400 centipoise(against 410 centipoise) at 50 C., optical density in a 30-mm. cuvette,0.7 (against 1.1), filterability, 210 ml. (against 55 ml.). Acetylationof the thus-activated pulp is carried out at 50C. with the use ofacetyloxide in the acetic-acid medium, sulphuric acid being thecatalyst. The bath ratio is equal to 20, catalyst consumption, 2 percent of the pulp weight, acetic acid-to-acetyloxide ratio, 85:15.

With the herein-proposed activation method, a possibility is rendered ofextending the assortment of the semifinished products engaged in themanufacture of man-made fibres and films due to the use of low-gradecellulose.

EXAMPLE 8 Let us consider an exemplary embodiment of the treatmentprocess of fibrous materials aimed at acetylating the pulp to bechemically processed.

The fibrous suspension of a distintegrated pulp with a concentration upto 5 percent at a temperature of 30 40 C. is pumped from therecirculation tank into the reactor. A hydrodynamic cavitation field iscreated at the place of contraction of the suspension fiow to intensifythe acetylation process. The treatment takes 8-12 minutes to occur.

A catalyst is introduced in the suspension through the nozzles in theetfuser.

A non-preactivated pulp may be subjected to acetylation by the proposedmethod.

As a result of the treatment by the proposed method, highly substitutedcellulose triacetate is obtained, featuring the degree of polymerizationof about 500 which -15 times reduces the time spent for acetylation bythe known method.

EXAMPLE 9 Let us consider an exemplary embodiment of the treatmentprocess aimed at impregnating chopped straw and cane with solutions ofchemicals.

The suspension of chopped straw or cane with a concentration up to 8percent at 30-40 C. is pumped from the recirculation tank into thereactor. A hydrodynamic cavitation field is established at the place ofcontraction of the suspension How to intensify the impregnation process,the treatment period taking 3 to 5 minutes to occur.

An impregnation liquor of digester acid is introduced into thesuspension through the nozzles in the effuser.

As a result of the treatment by the proposed method, the permeability ofthe fibers is increased which favourably tells on the pulp cooking rate.The impregnation 14 method by this method substitutes the macerationprocess.

EXAMPLE 10 Let us consider an exemplary embodiment of the treatmentprocess of fibrous materials aimed at washing the cellulose to get itrid of chemical reagents.

The fibrous suspension with a concentration up to 4 percent at 2030 C.is pumped from the recirculation tank into the reactor. A hydrodynamiccavitation field is established at the place of contraction of thesuspension flow to intensify the Washing process. Washing time is 15 to20 minutes.

Wash water is introduced into the suspension through the nozzles in theetfuser. Upon the cavitation treatment, the pulp suspension isdehydrated by the known methods.

As a result of the treatment by the proposed method, washing time isreduced from 68 hours according to the known methods to 15-20 minutes.Simple construction and safe operation improve the labour conditions forthe attending personnel.

EXAMPLE 1 1 Let us consider an exemplary embodiment of the treatmentprocess of fibrous materials involved in mercerization of pulp.

The suspension of the pulp taken as a loose mass at a concentration upto 8 percent and a temperature of 30- 40 C., is pumped from therecirculation tank into the reactor. A hydrodynamic field is establishedat the place of contraction of the suspension flow to intensify themercerization process.

Caustic soda is fed into the suspension through the nozzles in theeffuser. The process takes 4 to 5 minutes to take place. Under theeffect of the cavitation field possessing high erosion activity,conditions are established for a uniform swelling of the pulp and acomplete dissolving of hemicelluloses.

As a result of the treatment by the proposed method, the quality of thefinished product is improved and the content of the hemicellulosetherein is increased. Thus, when treating the pulp in a caustic-sodasolution with a concentration of 220 g./l. and the bath ratio of 20, thecontent of hemicellulose equals 2832 g./l. in the working solution and3035 g./l. in the pressed-up solution.

EXAMPLE 12 Let us consider an exemplary embodiment of the process ofdissolving cellulose xanthate.

The suspension of cellulose xanthate is pumped from the recirculationtank into the reactor. A solvent is introduced into the suspensionthrough the nozzles in the effuser. A hydrodynamic cavitation field isestablished at the place of contraction of the suspension flow tointensity the process of a deep penetration of the solvent inside thepolymer and destruction of the intermolecular bonds which contributes toa faster passing of xanthate into solution.

As a result of the treatment by the proposed method, a completedissolution of cellulose xanthate within 20 minutes occurs, with theresultant easy-to-filter viscose solution with a viscosity of 50 sec. asmeasured by the ball method and a 9.5-percent cellulose and 6.7-percentcaustic soda content.

EXAMPLE 13 Let us consider an exemplary embodiment of the treatmentprocess of fibrous materials involved in dyeing the paper mass.

The suspension of the material to be dyed with a concentration up to 4percent is pumped from the recirculation tank into the reactor. Amineral pigment is introduced into the suspension through the nozzles inthe effuser. A hydrodynamic cavitation field is established at the placeof contraction of the suspension flow to intensify the process of dyeingthe paper mass. Under the ef fect .of the cavitation field, a dispersionof the pigment and a uniform intermixing thereof with the material beingdyed take place.

As a result of the treatment by the proposed method, the quality andproperties of the paper from such paper mass, as well as its aestheticcharacteristics are substantially enhanced. When the suspension offibrous materials is treated by the now-existing methods, papercastings, feature a fairly number of visible inclusions of aggregatedparticles 0.08-04 mm. in size, while the castings of the cellulosetreated in the cavitation field wtihin the period of time twice asshort, incorporate no inclusions of the pigment.

EXAMPLE 14 Let us consider an exemplary embodiment of the treatmentprocess of the suspension of fibrous materials when defiocculating thepaper mass.

The suspension of paper mass with a concentration up to 4 percent at15-20 C. is pumped from the recirculation tank into the cavitationreactor. A hydrodynamic cavitation field is established at the place ofcontraction of the suspension flow under the effect of which theagglomerates of fibres formed Within the previous production processes,are dispersed.

The fibres of the paper mass, due to their having been charged with thelike potential, in the cavitation field forms no flocs during furtherflow of the suspension. Thus, the paper mass is ready for casting on apaper machine. With a 5-fold recirculation, the content of agglomeratesin the fibrous mass is 70-80 percent as low as that in the known methodsof treatment.

EXAMPLE 15 Let us consider an exemplary embodiment of the treatmentprocess of the suspension of fibrous materials when cleaning waste waterof pulp-and-paper industry.

The stream of waste water containing fine fibres, is fed from therecirculation tank into the cavitation reactor. Air is introduced intothe Waste water through the nozzles in the eifuser. A hydrodynamiccavitation field is established at the place of contraction of the wastewater flow to intensify the process of saturating the waste water withfine-disperse air bubbles. Under the influence of pressure pulsesarising during the closing of cavitation bubbles, the dispersing of thefibres being floated occurs as well as oversaturation of the suspensionwith air and dispersing large-sized air bubbles. An intense stirring ofthe suspension due to high degree of the flow turbulence in thecaviation field adds to the foam formation. The separated mass of thefine-disperse air bubbles float up within the zone of laminar flow andentrain the particles of fibres contained in the waste water. Theascended layer of the substances being floated is then separated fromthe larified water.

As a result of the treatment by the proposed method of waste watercontaining acid, neutral or alkaline medium without the use of anyflotation chemicals, a 5-6 percent increase in the concentration of thesubstances being floated is attained. Besides, the time spent for theprocess is cut down by 2 times as compared to the nowexisting methods.

The afore-considered examples testify to the fact that the treatment ofsuspensions of fibrous materials in a hydrodynamic cavitation fieldmakes it possible to considerably intensify the majority oftechnological processes involved in pulp-and-paper industry, enablessaid processes to be run with the use of novel equipment at adrastically reduced expense for the manufacture and operation ofproduction apparatus, allows high-quality products to be obtained atlower consumption of raw materials, power and time per unit of thefinished product. The fact that the proposed method runs continuouslyand is simple to be carried out enable a possibility of a completeautomation of the production process.

What is claimed is:

1. A method of treating suspension of fibrous materials, comprising anon-streamlined cylindrical solid body transversely in an elongatedpassageway in the hydrodynamic flow'of the suspension under treatment soas to cause a two-dimensional plane contraction of the How to producecavitation forces in the thus-contracting flow and in the wake at therear of the cylindrical surface of said non-streamlined body whichcavitation forces act upon the suspension of fibrous materials.

2. A method as claimed in claim 1, comprising introducing chemicalactivators for the treatment process are introduced into the flow ofsuspension upstream of the contraction thereof.

3. A method as claimed in claim 2, wherein for deresinating the fibrousmaterials, dispersants in an amount of 0.5 to 1.0 percent of the fibreWeight are introduced into the flow of suspension upstream of thecontraction thereof.

4. A method as claimed in claim 2, wherein for bleaching the fibrousmaterials, bleaching agents are introduced into the flow of suspensionupstream of the contraction thereof.

5. A method as claimed in claim 2, wherein for chlori mating the fibrousmaterials, gaseous chlorine is introduced into the flow of suspensionupstream of the contraction thereof.

6. A method of treating suspensions of fibrous materials, comprisingintroducing surfactants into the flow of suspension to enhance thereactive capacity of the fibrous materials of such suspensions,positioning a non-streamlined cylindrical solid body transversely in anelongated passageway in the hydrodynamic flow of the suspension undertreatment so as to cause a two-dimensional plane contraction of the flowto produce cavitation forces in the contracting flow and in the wake atthe rear of the cylindrical surface of said non-streamlined body whichcavitation forces act upon the suspension of fibrous materials.

7. A method of treating suspensions of fibrous materials, comprisingintroducing inclusion substances into the flow ofsuspension to activatethe fibrous materials of such suspension, positioning a non-streamlinedcylindrical solid body transversely in an elongated passageway in thehydrodynamic flow of the suspension under treatment so as to cause atwo-dimensional plane contraction of the flow to produce cavitationforces in the contracting flow and in the wake at the rear of thecylindrical surface of said non-streamlined body which cavitation forcesact upon the suspension of fibrous materials.

8. A method of treating suspensions of fibrous materials, comprisingintroducing catalysts into the flow of suspension to activate thefibrous materials of such suspension, positioning a non-streamlinedcylindrical solid body transversely in an elongated passageway in thehydrodynamic flow of the suspension under treatment so as to cause atwo-dimensional plane contraction of the flow to produce cavitationforces in the contracting fiow and in the wake at the rear of thecylindrical surface of said non-streamlined body which cavitation forcesact upon the suspension of fibrous materials.

9. A method of treating suspensions of fibrous materials, comprisingintroducing an impregnating solution into the flow of suspension,positioning a non-streamlined cylindrical solid body transversely in anelongated passageway in the hydrodyamic flow of the suspension undertreatment so as to cause a two-dimensional plane contraction of the flowto produce cavitation forces in the contraction flow and in the wake atthe rear of the cylindrical surface of said non-streamlined body whichcavitation forces act upon the suspension of fibrous materials.

10. A method of treating suspensions of fibrous materials, comprisingintroducing water into the flow of suspension to wash the fibrousmaterials of such suspension, positioning a non-streamlined cylindricalsolid body transversely in an elongated passageway in the hydrodynamicflow of the suspension under treatment so as to cause a two-dimensionalplane contraction of the flow to produce cavitation forces in thecontracting flow and in the wake at the rear of the cylindrical surfaceof said non-stream lined body which cavitation forces act upon thesuspension of fibrous materials.

11. A method of treating suspensions of fibrous materials, comprisingintroducing alkali into the flow of suspension to mercerize the fibrousmaterials of such suspension, positioning a non-streamlined cylindricalsolid body transversely in an elongated passageway in the hydrodynamicflow of the suspension under treatment so as to cause a two-dimensionalplane contraction of the flow to produce cavitation forces in thecontracting flow and in the wake at the rear of the cylindrical surfaceof said non-streamlined body which cavitation forces act upon thesuspension of fibrous materials.

12. A method of treating suspensions of fibrous materials, comprisingintroducing solvents into the flow of suspension for dissolving xanthatein the suspension, positioning a non-streamlined cylindrical solid bodytransversely in an elongated passageway in hydrodynamic fiow of thesuspension under treatment so as to cause a twodimensional planecontraction of the flow to produce cavitation forces in the contractingflow and in the wake at the rear of the cylindrical surface of saidnon-streamlined body which cavitation forces act upon the suspension offibrous materials.

13. A method of treating suspensions of fibrous materials, comprisingintroducing pigments into the flow of suspension to dye the fibrousmaterials in such suspension, positioning a non-streamlined cylindricalsolid body transversely in an elongated passageway in the hydrodynamicfiow of the suspension under treatment so as to cause a two-dimensionalplane contraction of the flow to produce cavitation forces in thecontracting flow and in the wake at the rear of the cylindrical surfaceof said nonstreamlined body which cavitation forces act upon thesuspension of fibrous materials.

14. A method of treating suspensions of fibrous materials, comprisingintroducing air to cleanse waste water of the fibrous material of suchsuspension positioning a non-streamlined cylindrical solid bodytransversely in an elongated passageway in the hydrodynamic flow of thesuspension under treatment so as to cause a two-dimensional planecontraction of the flow to produce cavitation forces in the contractingflow and in the wake at the rear of the cylindrical surface of saidnon-streamlined body which cavitation forces act upon the suspension offibrous materials.

15. An apparatus for treating suspensions of fibrous materials,comprising: a reactor including an elongated shell having an entranceand an exit; a non-streamlined solid cylindrical member located in thereactor shell adjacent its entrance at equal distances from the lateralwalls thereof; a first means to feed suspension into the reactor andcontinuously therethrough; an effuser which connects the reactor at saidentrance with said first means; a second means to continuously dischargethe treated suspension: and a diffuser which connects the reactor atsaid exit with said second means to remove the treated suspension; saidcylindrical member being so positioned in the reactor shell that thegeneratrix of the cylindrical surface of said member is normal to thedirection of flow of the suspension whereby said cylindrical memberproduces su stantial hydrodynamic cavitation in the wake at the rear ofsaid cylindrical surface of said non-streamlined member.

16. An apparatus as claimed in claim 15, comprising nozzles at the inletof the effuser located around the periphery thereof and adapted to feedchemical reagents into the flow of suspension of the fibrous materials.

17. An apparatus as claimed in claim 15, comprising a cylindricalsurface of the said cylindrical member a layer of an elastic material.

18. An apparatus as claimed in claim 15, comprising a pickup in saidreactor for measuring the erosion activity of a cavitation fieldproduced by said cylindrical member.

19. An apparatus as claimed in claim 15 wherein said elongatedpassageway has a rectangular cross-section.

References Cited UNITED STATES PATENTS 3,420,454 1/1969 Brown, Jr.162-5O FOREIGN PATENTS 268,162 10/1970 U.S.S.R. 16250 OTHER REFERENCESWilliams et al., Some Factors Affecting the Inception of Cavitation,Symposium held at Natl Phys. Lab. on Sept. 14-17, 1955, StimulateInterest in Ultrasonics for Wood Industries, Pulp and Paper, vol. 35,No. 1 (1961), p. 64.

S. LEON BASHORE, Primary Examiner P. CHIN, Assistant Examiner US. 01.X.R.

